U.S. patent application number 15/770196 was filed with the patent office on 2018-11-01 for magnetic sensor.
This patent application is currently assigned to TDK Corporation. The applicant listed for this patent is TDK CORPORATION. Invention is credited to Takato FUKUI.
Application Number | 20180313907 15/770196 |
Document ID | / |
Family ID | 58695032 |
Filed Date | 2018-11-01 |
United States Patent
Application |
20180313907 |
Kind Code |
A1 |
FUKUI; Takato |
November 1, 2018 |
MAGNETIC SENSOR
Abstract
An object of the present invention is to provide a magnetic
sensor capable of supporting a magnetic member in a stable manner,
even when a magnetic member with a large length in a direction
perpendicular to an element-forming surface is used. A magnetic
sensor includes a sensor chip 30 including an element-forming
surface 31 provided with a magnetism detection elements MR1-MR4, a
magnetic member 40 including a first side surface 41 facing the
element-forming surface 31, and a circuit board 20 including a
mounting surface 21 on which the sensor chip 30 and the magnetic
member 40 are mounted. The sensor chip 30 and the magnetic member
40 are mounted on the circuit board such that the element-forming
surface 31 and the first side surface 41 are substantially
orthogonal to the mounting surface 21 of the circuit board 20.
According to the present invention, because the sensor chip 30 and
the magnetic member 40 are mounted on the circuit board 20 in a
horizontal state, the magnetic member 40 can be supported in a
stable manner even when the length of the magnetic member 40 is
large.
Inventors: |
FUKUI; Takato; (TOKYO,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TDK CORPORATION |
TOKYO |
|
JP |
|
|
Assignee: |
TDK Corporation
TOKYO
JP
|
Family ID: |
58695032 |
Appl. No.: |
15/770196 |
Filed: |
October 20, 2016 |
PCT Filed: |
October 20, 2016 |
PCT NO: |
PCT/JP2016/081105 |
371 Date: |
April 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 33/0005 20130101;
G01R 33/09 20130101; G01R 33/0011 20130101; G01R 33/02
20130101 |
International
Class: |
G01R 33/00 20060101
G01R033/00; G01R 33/09 20060101 G01R033/09 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2015 |
JP |
2015-219451 |
Claims
1. A magnetic sensor comprising: a sensor chip including an
element-forming surface provided with a magnetism detection
element; a magnetic member including a first side surface facing
the element-forming surface; and a circuit board including a
mounting surface on which the sensor chip and the magnetic member
are mounted, wherein the sensor chip and the magnetic member are
mounted on the circuit board such that the element-forming surface
and the first side surface are substantially orthogonal to the
mounting surface of the circuit board.
2. The magnetic sensor as claimed in claim 1, wherein the magnetic
member further includes a second side surface substantially
parallel to the first side surface and located on an opposite side
of the first side surface, and wherein an area of the second side
surface is larger than an area of the first side surface.
3. The magnetic sensor as claimed in claim 2, wherein a length of
the second side surface in a direction perpendicular to the
mounting surface is larger than a length of the first side surface
in the direction perpendicular to the mounting surface.
4. The magnetic sensor as claimed in claim 1, wherein the magnetism
detection element includes first to fourth magnetoresistive
elements, wherein the first and second magnetoresistive elements
are located on one side as viewed from the first side surface of
the magnetic member, and wherein the third and fourth
magnetoresistive elements are located on other side as viewed from
the first side surface of the magnetic member.
5. The magnetic sensor as claimed in claim 4, further comprising an
auxiliary magnetic member mounted on the circuit board, wherein the
sensor chip further includes first and second side surfaces
substantially orthogonal to the element-forming surface and located
respectively on the one side and the other side as viewed from the
first side surface of the magnetic member, and wherein the
auxiliary magnetic member is mounted on the circuit board so as to
cover at least a part of the first and second side surfaces.
Description
TECHNICAL FIELD
[0001] The present invention relates to a magnetic sensor, and
particularly relates to a magnetic sensor including a magnetic
member for concentrating magnetic flux to a sensor chip.
BACKGROUND ART
[0002] Magnetic sensors using a magnetoresistive element or the
like are widely used in ammeters, magnetic encoders, and the like.
There is a case where magnetic sensors are provided with a magnetic
member for concentrating magnetic flux to a sensor chip. In this
case, the magnetic member is placed on an element-forming surface
of the sensor chip (see Patent Document 1).
CITATION LIST
Patent Document
[0003] Patent Document 1: Japanese Patent Application Laid-open No.
2009-276159
SUMMARY OF INVENTION
Technical Problem to be Solved by Invention
[0004] However, because sensor chips are generally small, placing a
magnetic member on a sensor chip is not easy, and reliably fixing a
sensor chip and a magnetic member has been difficult. Particularly,
when a magnetic member with a large length in a direction
perpendicular to an element-forming surface is used, the support on
a sensor chip becomes highly unstable, possibly causing the
magnetic member to fall or bend in some cases.
[0005] Therefore, an object of the present invention is to provide
a magnetic sensor capable of supporting a magnetic member in a
stable manner, even when a magnetic member with a large length in a
direction perpendicular to an element-forming surface is used.
Means for Solving Problem
[0006] A magnetic sensor according to the present invention
includes a sensor chip including an element-forming surface
provided with a magnetism detection element, a magnetic member
including a first side surface facing the element-forming surface,
and a circuit board including a mounting surface on which the
sensor chip and the magnetic member are mounted, wherein the sensor
chip and the magnetic member are mounted on the circuit board such
that the element-forming surface and the first side surface are
substantially orthogonal to the mounting surface of the circuit
board.
[0007] According to the present invention, because the sensor chip
and the magnetic member are mounted on the circuit board in a
horizontal state, the magnetic member can be supported in a stable
manner even when the length of the magnetic member is large.
[0008] In the present invention, it is preferable that the magnetic
member further includes a second side surface substantially
parallel to the first side surface and located on an opposite side
of the first side surface, and an area of the second side surface
is larger than an area of the first side surface. Accordingly,
because more magnetic flux can be concentrated, the sensitivity of
the magnetic sensor can be enhanced. In this case, a length of the
second side surface in a direction perpendicular to the mounting
surface can be larger than a length of the first side surface in
the direction perpendicular to the mounting surface.
[0009] In the present invention, it is preferable that the
magnetism detection element includes first to fourth
magnetoresistive elements, wherein the first and second
magnetoresistive elements are located on one side as viewed from
the first side surface of the magnetic member, and the third and
fourth magnetoresistive elements are located on the other side as
viewed from the first side surface of the magnetic member. With
this configuration, a bridge circuit using the four
magnetoresistive elements is formed, thereby allowing magnetism
detection to be performed with high sensitivity.
[0010] In this case, it is preferable that the magnetic sensor
according to the present invention further includes an auxiliary
magnetic member mounted on the circuit board, wherein the sensor
chip further includes first and second side surfaces substantially
orthogonal to the element-forming surface and located respectively
on the one side and the other side as viewed from the first side
surface of the magnetic member, and the auxiliary magnetic member
is mounted on the circuit board so as to cover at least a part of
the first and second side surfaces. With this configuration, the
magnetic flux input to the element-forming surface is curved in
directions of the first and second side surfaces, thereby allowing
magnetism detection to be performed with even higher
sensitivity.
Advantageous Effects of Invention
[0011] According to the present invention, it is possible to
provide a magnetic sensor capable of supporting a magnetic member
in a stable manner, even when a magnetic member with a large length
in a direction perpendicular to an element-forming surface is
used.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a schematic perspective view illustrating an
external appearance of a magnetic sensor 10 according to a
preferred embodiment of the present invention.
[0013] FIG. 2 is an exploded perspective view of the magnetic
sensor 10.
[0014] FIG. 3 is a partial enlarged view of the magnetic sensor
10.
[0015] FIG. 4 is a circuit diagram for explaining a connecting
relation between the terminal electrodes E11 to E14 and the
magnetism detection elements MR1 to MR4.
[0016] FIG. 5 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10A according to a first
modification.
[0017] FIG. 6 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10B according to a second
modification.
[0018] FIG. 7 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10C according to a third
modification.
[0019] FIG. 8 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10D according to a fourth
modification.
[0020] FIG. 9 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10E according to a fifth
modification.
[0021] FIG. 10 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10F according to a sixth
modification.
[0022] FIG. 11 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10G according to a seventh
modification.
MODE FOR CARRYING OUT THE INVENTION
[0023] Preferred embodiments of the present invention will now be
explained in detail with reference to the drawings.
[0024] FIG. 1 is a schematic perspective view illustrating an
external appearance of a magnetic sensor 10 according to the
preferred embodiment of the present invention. FIG. 2 is an
exploded perspective view of the magnetic sensor 10.
[0025] As illustrated in FIGS. 1 and 2, the magnetic sensor 10
according to the present invention is constituted by a circuit
board 20 and a sensor chip 30 and a magnetic member 40 mounted on a
mounting surface 21 of the circuit board 20.
[0026] The circuit board 20 is a board in which a wiring pattern is
formed on an insulating base of resin or the like, and a general
printed circuit board or interposer circuit board can be used
therefor. The mounting surface 21 of the circuit board 20 forms an
xy surface, and the mounting surface 21 has the sensor chip 30 and
the magnetic member 40 mounted thereon. Four land patterns E21 to
E24 are provided on the mounting surface 21 of the circuit board
20. A constant voltage source and a voltage detection circuit
described later are connected to the land patterns E21 to E24. The
constant voltage source and the voltage detection circuit can be
provided on the circuit board 20 itself or can be provided on
another circuit board that is different from the circuit board
20.
[0027] The sensor chip 30 has a substantially rectangular cuboid
shape, and four magnetism detection elements MR1 to MR4 are formed
on an element-forming surface 31. As illustrated in FIGS. 1 and 2,
the element-forming surface 31 forms an xz surface. That is, the
sensor chip 30 is mounted horizontally such that the
element-forming surface 31 is substantially orthogonal to the
mounting surface 21 of the circuit board 20.
[0028] While the sensor chip 30 is fixed to the circuit board 20,
the bottom surface (the xy surface) of the sensor chip 30 and the
mounting surface 21 of the circuit board 20 do not need to be in
close contact, and there can be an adhesive applied between the two
surfaces. As illustrated in FIG. 3, which is an enlarged view, it
is permissible that an adhesive G provided in a partial manner
fixes the bottom surface (the xy surface) of the sensor chip 30 and
the mounting surface 21 of the circuit board 20 to each other while
leaving a slight gap existing therebetween.
[0029] The magnetism detection elements MR1 to MR4 are not
particularly limited to any type as long as the elements change in
physical characteristics depending on the magnetic flux density. In
the present embodiment, magnetoresistive elements (MR elements)
that change in the electrical resistance according to the direction
of a magnetic field are used. The fixed directions of magnetization
of the magnetism detection elements MR1 to MR4 are all aligned in a
direction (to the plus side in the x-direction) indicated by an
arrow A in FIG. 2. A large number of the sensor chips 30 are
produced by using an aggregate board, so that multiple pieces are
obtained by dicing. In this manner, in the present embodiment, the
sensor chip 30 resulting from the dicing is mounted on the circuit
board 20 at 90.degree. in a horizontal state.
[0030] Further, four terminal electrodes E11 to E14 are provided on
the element-forming surface 31 of the sensor chip 30. The terminal
electrodes E11 to E14 are respectively connected to the land
patterns E21 to E24 via solder S. The connecting relation between
the terminal electrodes E11 to E14 and the magnetism detection
elements MR1 to MR4 are described below.
[0031] The magnetic member 40 is a block formed of a high
permeability material such as ferrite, and is in a substantially
rectangular cuboid shape in the present embodiment. An xz surface
of the magnetic member 40 forms a first side surface 41 facing the
element-forming surface 31 of the sensor chip 30. The area of the
first side surface 41 is smaller than the area of the
element-forming surface 31 of the sensor chip 30 and is mounted on
the circuit board 20 to face an opposing region 31a located between
the magnetism detection elements MR1 and MR2 and the magnetism
detection elements MR3 and MR4. The first side surface 41 of the
magnetic member 40 and the opposing region 31a of the sensor chip
30 can be in close contact with each other, or there can be a
slight gap existing between the two elements. Note that, in the
present embodiment, the sensor chip 30 and the magnetic member 40
do not need to be fixed by an adhesive or the like, because the
sensor chip 30 and the magnetic member 40 are both placed on the
mounting surface 21 of the circuit board 20.
[0032] While the magnetic member 40 is fixed to the circuit board
20, the bottom surface (the xy surface) of the magnetic member 40
and the mounting surface 21 of the circuit board 20 do not need to
be in close contact, and there can be an adhesive applied between
the two surfaces. As illustrated in FIG. 3, which is an enlarged
view, it is permissible that the adhesive G provided in a partial
manner fixes the bottom surface (the xy surface) of the magnetic
member 40 and the mounting surface 21 of the circuit board 20 to
each other while leaving a slight gap existing therebetween.
[0033] While the length of the magnetic member 40 in the
y-direction is not particularly limited to any length, increasing
the length in the y-direction can enhance the selectivity of the
magnetic flux in the y-direction. Because the y-direction is
parallel to the mounting surface 21 of the circuit board 20 in the
present embodiment, increasing the length of the magnetic member 40
in the y-direction does not cause the support of the magnetic
member 40 to become unstable.
[0034] FIG. 4 is a circuit diagram for explaining a connecting
relation between the terminal electrodes E11 to E14 and the
magnetism detection elements MR1 to MR4.
[0035] As illustrated in FIG. 4, the magnetism detection element
MR1 is connected between the terminal electrodes E11 and E13, the
magnetism detection element MR2 is connected between the terminal
electrodes E12 and E14, the magnetism detection element MR3 is
connected between the terminal electrodes E12 and E13, and the
magnetism detection element MR4 is connected between the terminal
electrodes E11 and E14. A predetermined voltage is applied between
the terminal electrodes E11 and E12 by a constant voltage source
51. A voltage detection circuit 52 is connected between the
terminal electrodes E13 and E14 to accordingly detect the level of
an output voltage that appears between the terminal electrodes E13
and E14.
[0036] The magnetism detection elements MR1 and MR2 are arranged on
one side (the minus side in the x-direction) as viewed from the
opposing region 31a, and the magnetism detection elements MR3 and
MR4 are arranged on the other side (the plus side in the
x-direction) as viewed from the opposing region 31a. Therefore, the
magnetism detection elements MR1 to MR4 forms a differential bridge
circuit, allowing a change in the electrical resistance of the
magnetism detection elements MR1 to MR4 to be detected with high
sensitivity according to the magnetic flux density.
[0037] Specifically, the magnetic flux in a direction (to the plus
side in the y-direction) indicated by an arrow B in FIG. 1 is
mainly drawn toward a second side surface 42 of the magnetic member
40, passes through the inside of the magnetic member 40 in the
y-direction, and then is output mainly from the first side surface
41. The magnetic flux output from the first side surface 41 moves
around the both sides in the x-direction and returns to an
originating source of the magnetic flux. At this time, the
magnetism detection elements MR1 to MR4 all have the same fixed
direction of magnetization. Therefore, a difference occurs between
the amount of change in the resistance of the magnetism detection
elements MR1 and MR2 located on one side as viewed from the
opposing region 31a and the amount of change in the resistance of
the magnetism detection element MR3 and MR4 located on the other
side as viewed from the opposing region 31a. The difference is
amplified and doubled by the differential bridge circuit
illustrated in FIG. 4 and is detected by the voltage detection
circuit 52.
[0038] In this manner, the magnetic sensor 10 according to the
present embodiment can detect the magnetic flux density in the
y-direction with the voltage detection circuit 52, because the
magnetic member 40 is arranged to oppose the element-forming
surface 31 of the sensor chip 30. Further, in the present
embodiment, because the element-forming surface 31 of the sensor
chip 30 is perpendicular to the mounting surface 21 of the circuit
board 20, increasing the length of the magnetic member 40 in the
y-direction does not cause the fixation of the magnetic member 40
to become unstable.
[0039] A modification of the magnetic sensor 10 according to the
present embodiment is described below.
[0040] FIG. 5 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10A according to the first
modification.
[0041] The magnetic sensor 10A illustrated in FIG. 5 differs from
the magnetic sensor 10 illustrated in FIG. 1 in that an auxiliary
magnetic member 60 mounted on the circuit board 20 is further
provided. The auxiliary magnetic member 60 is a block formed of a
high permeability material such as ferrite in a similar manner to
the magnetic member 40, and has a rectangular U-shape to cover the
xz surface other than the element-forming surface 31 and a yz
surface of the sensor chip 30. With this configuration, the
magnetic flux input to the element-forming surface 31 of the sensor
chip 30 via the magnetic member 40 is easily curved in the
x-direction. Therefore, the sensitivity of detection by the
magnetism detection elements MR1 to MR4 can be enhanced.
[0042] FIG. 6 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10B according to the second
modification.
[0043] The magnetic sensor 10B illustrated in FIG. 6 differs from
the magnetic sensor 10A illustrated in FIG. 5 in that the auxiliary
magnetic member 60 is replaced with two auxiliary magnetic members
71 and 72. The auxiliary magnetic members 71 and 72 are the
auxiliary magnetic member 60 without a portion covering the xz
surface of the sensor chip 30 located on the opposite side of the
element-forming surface 31. That is, it is a configuration in which
the auxiliary magnetic member 71 covers one of two yz surfaces of
the sensor chip 30 and the auxiliary magnetic member 72 covers the
other one. With this configuration, the magnetic flux input to the
element-forming surface 31 of the sensor chip 30 is more easily
curved in the x-direction, and thus the sensitivity of detection by
the magnetism detection elements MR1 to MR4 can be further
enhanced.
[0044] In the magnetic sensors 10A and 10B according to the first
and second modifications, the two yz surfaces of the sensor chip 30
are almost completely covered by the auxiliary magnetic member 60
or by the auxiliary magnetic members 71 and 72. However, it is also
possible that only a part of the yz surface is covered. In this
case, it is preferable to cover a portion closer to the
element-forming surface 31.
[0045] FIG. 7 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10C according to the third
modification.
[0046] The magnetic sensor 10C illustrated in FIG. 7 differs from
the magnetic sensor 10 illustrated in FIG. 1 in the shape of the
magnetic member 40. The magnetic sensor 10C illustrated in FIG. 7
has a tapered shape in which the width of the magnetic member 40 in
the x-direction gradually increases from the first side surface 41
toward the second side surface 42. Accordingly, more magnetic flux
in the y-direction can be concentrated, because the area of the
second side surface 42 is larger than the area of the first side
surface 41. As a result, the sensitivity of detection by the
magnetism detection elements MR1 to MR4 can be enhanced.
[0047] When the element-forming surface 31 is parallel to the
mounting surface 21 of the circuit board 20, using the magnetic
member 40 having such a shape causes the support of the magnetic
member 40 to become highly unstable. However, because the sensor
chip 30 is mounted on the circuit board 20 in a horizontal state in
the present embodiment, such a problem does not occur. The fixation
of the magnetic member 40 rather becomes more stable, because the
area in which the magnetic member 40 is placed with respect to the
circuit board 20 increases. In the magnetic sensor 10C illustrated
in FIG. 7, the width of the magnetic member 40 in the x-direction
increases throughout the entire region in the y-direction. However,
it is permissible to have a shape that the width of the magnetic
member 40 in the x-direction is constant up to a certain length in
the y-direction from the first side surface 41, and the width in
the x-direction increases in the remaining portion.
[0048] FIG. 8 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10D according to the fourth
modification.
[0049] The magnetic sensor 10D illustrated in FIG. 8 differs from
the magnetic sensor 10C illustrated in FIG. 7 in the tapered shape
in which the height of the magnetic member 40 in the z-direction
gradually increases from the first side surface 41 toward the
second side surface 42. Also with such a shape, more magnetic flux
in the y-direction can be concentrated, because the area of the
second side surface 42 is larger than the area of the first side
surface 41. It is not necessary that both of the width in the
x-direction and the height in the z-direction of the magnetic
member 40 are increased in a tapered manner. For example, it is
permissible that only the height of the magnetic member 40 in the
z-direction increases in a tapered manner.
[0050] FIG. 9 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10E according to the fifth
modification.
[0051] The magnetic sensor 10E illustrated in FIG. 9 differs from
the magnetic sensor 10 illustrated in FIG. 1 in the shape of the
magnetic member 40. In the magnetic sensor 10E illustrated in FIG.
9, the magnetic member 40 has a T-shape in planar view (as viewed
from the z-direction). In other words, it is a shape that the width
of the magnetic member 40 in the x-direction increases at once.
Accordingly, more magnetic flux in the y-direction can be
concentrated, because the area of the second side surface 42 is
larger than the area of the first side surface 41. In this manner,
when the width of the magnetic member 40 in the x-direction is
increased, it is not necessary that the increase is made in a
tapered manner, and the shape can be such that the increase made at
once. Alternatively, it is permissible to have a shape that the
width of the magnetic member 40 in the x-direction increases in a
step-wise manner from the first side surface 41 toward the second
side surface 42.
[0052] FIG. 10 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10F according to the sixth
modification.
[0053] The magnetic sensor 10F illustrated in FIG. 10 differs from
the magnetic sensor 10E illustrated in FIG. 9 in that the height in
the z-direction of a portion forming the second side surface 42 of
the magnetic member 40 increases. With such a shape, more magnetic
flux in the y-direction can be concentrated, because the area of
the second side surface 42 becomes even larger.
[0054] FIG. 11 is a schematic perspective view illustrating a
configuration of a magnetic sensor 10G according to the seventh
modification.
[0055] The magnetic sensor 10G illustrated in FIG. 11 differs from
the magnetic sensor 10 illustrated in FIG. 1 in the shape of the
magnetic member 40. In the magnetic sensor 10G illustrated in FIG.
11, the magnetic member 40 has a Y-shape in planar view (as viewed
from the z-direction). In other words, the magnetic member 40 has a
shape bifurcating from the first side surface 41 toward the second
side surface 42. Accordingly, more magnetic flux in the y-direction
can be concentrated, because the area of the second side surface 42
is, for example, double the area of the first side surface 41. In
this manner, the second side surface 42 can be provided in
plural.
[0056] It is apparent that the present invention is not limited to
the above embodiments, but may be modified and changed without
departing from the scope and spirit of the invention.
[0057] For example, in the embodiment described above, four
magnetoresistiveelements (MR elements) are used as magnetism
detection elements; however, the type and number of the magnetism
detection elements are not particularly limited to any specific
one.
REFERENCE SIGNS LIST
[0058] 10, 10A-10G: magnetic sensor
[0059] 20: circuit board
[0060] 21: mounting surface
[0061] 30: sensor chip
[0062] 31: element-forming surface
[0063] 31a: opposing region
[0064] 40: magnetic member
[0065] 41: first side surface
[0066] 42: second side surface
[0067] 51: constant voltage source
[0068] 52: voltage detection circuit
[0069] 60, 71, 72: auxiliary magnetic member
[0070] E11-E14: terminal electrode
[0071] E21-E24: land pattern
[0072] G: adhesive
[0073] MR1-MR4: magnetism detection element
[0074] S: solder
* * * * *